A few studies reported detectable levels of the enzymes involved in the generation of DHEA from cholesterol (StAR, CYP11A1 and CYP17A1) in endometriosis (Tsai et al., 2001; Rhee et al., 2003; Bukulmez et al., 2008a; Attar et al., 2009; Sinreih et al., 2013, 2017b; Huhtinen et al., 2014), suggesting that, in contrast to eutopic endometrium, endometriosis is able to produce steroids from cholesterol. The gene discussed is CYP17A1; the disease is endometriosis.